JP4513861B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus that purifies particulate matter in exhaust gas discharged from a diesel engine by collecting and oxidizing the exhaust gas.

In general, exhaust gas of a diesel engine contains particulate matter containing carbon as a main component (hereinafter referred to as PM (Particulate Matter)) and is known to cause air pollution. Therefore, various apparatuses or methods for capturing and removing these particulate substances from exhaust gas have been proposed.
For example, by forcing and supplying fuel, the temperature of a diesel particulate filter (DPF) is raised to oxidize and burn the collected PM, and nitrogen dioxide NO ₂ from nitrogen monoxide NO in exhaust gas A catalyst that oxidizes PM with NO ₂ (for example, Japanese Patent Application Publication No. 2002-531762) or a catalyst that oxidizes PM using a catalyzed DPF (for example, Japanese Patent Application Laid-Open Nos. Hei 6-272541, 9-125931) and the like have been proposed. However, in the case where the fuel is forcibly supplied by injection, the fuel consumption is deteriorated and the problem of the DPF breakage due to the temperature rise as a result of the rapid combustion of PM, as described in JP 2002-53762 A, Since the oxidation rate of PM by NO ₂ is not sufficient, it is difficult to completely oxidize and remove PM discharged from the engine, and JP-A-6-275441 and JP-A-9-125931. In the case of using the catalyzed DPF described in (2), since both the catalyst and PM are solid, there is a problem that the two do not sufficiently contact each other and the oxidation reaction of PM is insufficient.
Therefore, recently, a technique for oxidizing and treating PM using ozone O ₃ having a stronger oxidizing power than NO ₂ has been disclosed (for example, JP-A-2005-502823). In the method and apparatus for post-processing exhaust gas of a diesel engine described in Japanese Patent Application Laid-Open No. 2005-502823, ozone or NO ₂ as an oxidant is generated from the exhaust gas by plasma upstream of the particulate filter. the apparatus is provided, in accordance with the temperature of the exhaust gas, at low temperatures the ozone and NO _2, by using selectively the NO ₂ at high temperatures, and to oxidize and remove soot collected in the particulate filter.
By the way, in the method and apparatus for post-processing exhaust gas of a diesel engine described in Japanese Patent Application Laid-Open No. 2005-502823, ozone having stronger oxidizing power than NO ₂ is used. Can be evaluated. However, the one described in Japanese Patent Application Laid-Open No. 2005-502823 generates ozone by plasma from oxygen which is a component of exhaust gas, and introduces exhaust gas containing NOx and the like into the particulate filter together with the generated ozone. Therefore, it cannot be said that the amount of ozone generated is sufficient, and ozone with strong oxidizing power may be consumed by reacting with NOx in the exhaust gas before entering the particulate filter. However, there is a problem that the amount of ozone that can be used for PM oxidation removal decreases, sufficient purification efficiency cannot be obtained, and the oxidation rate of PM may decrease.
Therefore, an object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can efficiently use ozone when oxidizing and removing PM using ozone.

An exhaust gas purification apparatus for an internal combustion engine according to the present invention is branched and connected to an exhaust passage, and a plurality of particulate matter collection devices that collect particulate matter in exhaust gas, and the plurality of particulate matter collection devices Ozone supply means capable of supplying ozone to the upstream side, and control means for changing the ratio of the supply amount of exhaust gas and the ratio of supply amount of ozone between the plurality of particulate matter collection devices, It is characterized by providing.
According to the exhaust gas purification apparatus for an internal combustion engine, the ratio of the exhaust gas supply amount among the plurality of particulate matter collection devices can be changed. In the substance collection device, consumption of ozone by a predetermined substance such as NOx or HC in the exhaust gas can be suppressed, and decomposition of ozone due to heat of the exhaust gas can be suppressed. Therefore, ozone can be used efficiently, and PM purification efficiency by ozone can be improved.
The apparatus according to the present invention preferably further includes at least one catalyst device that is disposed in the exhaust passage upstream of the plurality of particulate matter trapping devices and removes a predetermined substance in the exhaust gas.
The apparatus according to the present invention includes a collection amount detection unit that individually detects a collection amount of the plurality of particulate matter collection devices, and a temperature detection unit that individually detects the temperature of the plurality of particulate matter collection devices. And the control means controls the ratio of the supply amount of the exhaust gas based on the collected amount detected by the collected amount detecting means, and based on the temperature detected by the temperature detecting means. The ratio of the ozone supply amount may be controlled. In this case, it is possible to preferentially execute PM oxidation removal for a particulate matter collection device that is highly required to be oxidized by PM.
It is preferable that the control means make the ratio of the amount of ozone supplied to the particulate matter collection device in which the ratio of the amount of exhaust gas supplied is relatively small relatively large. Here, “the proportion of the exhaust gas supply amount is relatively small” indicates a state in which the proportion of the exhaust gas supply amount is smaller than at least one of the other particulate matter collection devices. Similarly, “relatively increasing the ratio of the ozone supply amount” indicates that the ratio of the ozone supply amount is made larger than at least one of the other particulate matter collection devices.
The apparatus according to the present invention can individually fully close exhaust gas passages to the plurality of particulate matter collection devices and can individually individually close ozone passages to the plurality of particulate matter collection devices. Preferably there is.
The apparatus according to the present invention further includes a collection amount detection means for individually detecting the collection amounts of the plurality of particulate matter collection devices, and the control means is a capture device among the plurality of particulate matter collection devices. A particulate matter collecting device having a low collection amount may be selected as a supply destination of the exhaust gas. Here, “the collected amount is low” indicates a state where the collected amount is lower than at least one of the other particulate matter collecting devices.
The control means is configured to capture the particulate matter when the temperature of the particulate matter collection device having a relatively large collection amount among the plurality of particulate matter collection devices falls below a predetermined low temperature side reference value. When the ozone supply amount to the collector is set to a predetermined maximum amount and the temperature of the particulate matter collector exceeds the low temperature side reference value, the ozone supply amount to the particulate matter collector is exhausted. It may be set based on the NOx concentration in the medium. Here, “the collection amount is relatively large” indicates a state where the collection amount is larger than at least one of the other particulate matter collection devices.
When the temperature of the particulate matter collection device having a relatively large collection amount among the plurality of particulate matter collection devices falls below a predetermined low temperature side reference value, the control means You may select the comparatively small particulate matter collection apparatus as a supply destination of ozone. Here, “the amount of collection is relatively large” means that the amount of collection is larger than at least one of the other particulate matter collection devices, and “particulate matter with a relatively small amount of collection”. The “collecting device” refers to at least one particulate matter collecting device other than the particulate matter collecting device having a relatively large collection amount.
The control means may stop supplying ozone from the ozone supply means when the temperature exceeds a predetermined high temperature reference value.
In the apparatus according to the present invention, the plurality of particulate matter collection devices further include a temperature raising unit, and the control unit controls the temperature raising unit to be selected as an exhaust gas supply destination. When the temperature of the collection device exceeds a predetermined high temperature reference value, the particulate matter collection device may be heated.
When the apparatus according to the present invention includes at least one catalyst device, the apparatus further includes catalyst temperature detection means for detecting the temperature of the catalyst device, and the control means is configured to detect the ozone based on the temperature of the at least one catalyst device. It is preferable to control the supply means.
The apparatus according to the present invention is preferably provided with an exhaust control valve at a branch point of the exhaust passage that can change a ratio of an exhaust gas supply amount among the plurality of particulate matter collection devices.
The ozone supply means in the present invention preferably includes an ozone control valve capable of changing a ratio of the amount of ozone supplied from a single ozone supply source among the plurality of particulate matter collection devices.
According to another aspect of the present invention, there is provided a plurality of filter chambers in which the particulate matter collection device is formed in a single casing so as to be adjacent to each other and in parallel to the exhaust gas flow direction. A filter member disposed in each chamber, and valve means for switching the filter chamber through which exhaust gas flows, wherein the ozone supply means is disposed in each of the plurality of filter chambers, and the valve means includes the ozone supply It is preferably arranged upstream of the means.
According to this aspect of the present invention, the filter chamber in which ozone supply by the ozone supply means is executed can be closed by the valve means, and the inflow of exhaust gas into the filter chamber can be suppressed. Accordingly, wasteful consumption of the supplied ozone due to NOx or the like in the exhaust gas is prevented, and a larger amount of ozone can be used for the oxidation removal of PM deposited on the filter member. Therefore, it becomes possible to use ozone efficiently.
In this case, it is preferable that two filter chambers are formed at the center and the outer periphery of the casing.
The valve means is configured so that exhaust gas does not flow into the filter chamber where ozone supply from the ozone supply means is executed, and exhaust gas flows into the filter chamber where ozone supply from the ozone supply means is not executed. Preferably, the filter chamber is switched.
The valve means includes: a first valve body that opens and closes a part of the plurality of filter chambers; a second valve body that opens and closes the remaining filter chambers of the plurality of filter chambers; and ozone supply Corresponding to the filter chamber in which the first valve body and the second valve body are alternately opened and closed, the driving means for driving the first valve body and the second valve body is preferably provided. .
The apparatus of the present invention includes at least one temperature detecting means for detecting a gas flowing into at least one filter member or a temperature of the filter member, and the ozone corresponding to the filter member according to the detected temperature. It is preferable to provide a means for controlling the ozone supply from the supply means. When performing PM oxidation removal of the filter member with ozone, it is desirable that the gas flowing into the filter member or the temperature of the filter member is within an appropriate temperature range in which PM oxidation with ozone can be effectively performed. According to this preferable mode, ozone supply can be executed only when the detected temperature is within an appropriate temperature range, and supply ozone is prevented from being consumed in an inappropriate temperature range.
In this case, a cooling gas supply means that is disposed between the at least one filter member and the valve means and can supply a cooling gas from the upstream side to the filter member, and according to the detected temperature And means for controlling cooling gas supply from the cooling gas supply means. According to this preferred embodiment, when the temperature corresponding to the filter member that performs PM oxidation removal is higher than the appropriate temperature range, the cooling air is supplied from the air supply means, and the temperature is reduced to the appropriate temperature range. Can do. Thereby, ozone supply can be performed within an appropriate temperature range, and supply ozone is prevented from being consumed in an inappropriate temperature range.

FIG. 1 is a system diagram schematically showing an exhaust emission control device for an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a DPF wall-flow honeycomb structure.
FIG. 3A is a schematic diagram for explaining the mechanism of NOx absorption / release in the NOx storage reduction catalyst.
FIG. 3B is a schematic diagram for explaining the mechanism of NOx absorption / release in the NOx storage reduction catalyst.
FIG. 4 is a schematic view showing the structure of the selective reduction type NOx catalyst.
FIG. 5 is a flowchart showing an example of processing in the ECU of the first embodiment.
FIG. 6 is a diagram showing the entire experimental apparatus for experiments conducted in connection with the first embodiment.
FIG. 7 is a graph showing the experimental results of the experimental apparatus of FIG.
FIG. 8 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the second embodiment of the present invention.
FIG. 9 is a flowchart showing an example of processing in the ECU of the second embodiment.
FIG. 10 is a graph showing an experimental result of an experiment performed in connection with the second embodiment.
FIG. 11 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the third embodiment of the present invention.
FIG. 12 is a conceptual diagram illustrating a setting example of a temperature region in the third embodiment.
FIG. 13 is a flowchart showing an example of processing in the ECU of the third embodiment.
FIG. 14 is a conceptual diagram showing a modification of the first, second, or third embodiment.
FIG. 15 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the fourth embodiment of the present invention.
FIG. 16 is a side sectional view showing the filter member.
FIG. 17 is a schematic front view showing the central valve body and the outer peripheral valve body.
FIG. 18A is a schematic side view showing the drive device.
FIG. 18B is a schematic side view showing the driving device.
FIG. 19A is a diagram for explaining the operation of the exhaust purification apparatus of the fourth embodiment.
FIG. 19B is a diagram for explaining the operation of the exhaust purification apparatus of the fourth embodiment.
FIG. 20 is a graph showing the relationship between the temperature and the PM oxidation rate when performing PM oxidation with ozone.
FIG. 21 is a diagram showing the entire experimental apparatus.
FIG. 22 is a diagram illustrating a configuration of the first comparative example.
FIG. 23 is a graph showing experimental results according to the fourth embodiment.
FIG. 24 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the fifth embodiment of the present invention.
FIG. 25 is a graph showing experimental results according to the fifth embodiment.
FIG. 26 is a schematic front view of another embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.
  [First embodiment]
  FIG. 1 is a system diagram schematically showing an exhaust emission control device for an internal combustion engine according to a first embodiment of the present invention. In the figure, 10 is a compression ignition type internal combustion engine, that is, a diesel engine, 11 is an intake manifold communicated with an intake port, 12 is an exhaust manifold communicated with an exhaust port, and 13 is a combustion chamber. In the present embodiment, fuel supplied from a fuel tank (not shown) to the high pressure pump 17 is pumped to the common rail 18 by the high pressure pump 17 and accumulated in a high pressure state. The fuel is directly injected into the combustion chamber 13. Exhaust gas from the diesel engine 10 passes from the exhaust manifold 12 through the turbocharger 19 and then flows into the exhaust passage 15 downstream thereof. After being purified as described later, the exhaust gas is discharged to the atmosphere. In addition, as a form of a diesel engine, it is not restricted to the thing provided with such a common rail type fuel injection device. It is also optional to include other exhaust purification devices such as EGR devices.
  The exhaust passage 15 includes a NOx catalyst 20 for purifying NOx in the exhaust gas, and a diesel particulate filter (hereinafter referred to as DPF) as a particulate matter collection device for collecting the particulate matter (PM) in the exhaust gas. 30a, 30b). The DPFs 30a and 30b are branched and connected to the exhaust passage 15 on the downstream side of the NOx catalyst 20 via the exhaust control valve V1.
  In addition, ozone supply as ozone supply means capable of supplying ozone to the DPF 30a, 30b between the NOx catalyst 20 and the DPF 30a, 30b, in other words, downstream of the NOx catalyst 20 and the exhaust control valve V1 and upstream of the DPF 30a, 30b. Nozzles 40a and 40b are arranged. An ozone generator 41 as an ozone supply source is branched and connected to the ozone supply nozzles 40a and 40b via an ozone control valve V2. The ozone generated by the ozone generator 41 is supplied to the ozone supply nozzles 40a and 40b via the ozone control valve V2 and the ozone supply passages 42a and 42b, and is adjacent to the downstream side from the ozone supply nozzles 40a and 40b. Injected into the exhaust passage 15 toward the DPFs 30a and 30b.
  The ozone supply nozzles 40a and 40b are disposed at positions immediately upstream of the DPFs 30a and 30b so that the ozone injected and supplied from the ozone reacts with NOx and unburned components (CO, HC, etc.) in the exhaust gas and is not consumed by people. From there, ozone is supplied toward the DPFs 30a and 30b. Also, a plurality of ozone supply ports 41 are provided so as to cover the entire diameter of the upstream end faces of the DPFs 30a and 30b so that ozone can be supplied evenly to the entire upstream end faces of the DPFs 30a and 30b. The ozone supply nozzles 40a and 40b extend in the diameter direction of the casings 31a and 31b and are fixed to the casings 31a and 31b. The DPF 30a, the casing 31a, and the ozone supply nozzle 40a constitute a unit A. The DPF 30b, the casing 31b, and the ozone supply nozzle 40b constitute a unit B. The ozone supply means may have various forms other than the ozone supply nozzles 40a and 40b. For example, when only one ozone supply port is provided, the ozone supply port and the upstream end surface of the DPF. It is preferable that the distance between the two is separated by a distance that allows ozone to spread throughout the entire upstream end face.
  As the ozone generator 41, the form which generate | occur | produces ozone, flowing the dry air or oxygen used as a raw material in the discharge tube which can apply a high voltage, and the other arbitrary forms can be used. The dry air or oxygen used as the raw material here is a gas taken from outside the exhaust passage 15, for example, a gas contained in the outside air, unlike the case of Japanese Patent Laid-Open No. 2005-502823. It is not a gas contained in the exhaust gas inside. In the ozone generator 41, ozone generation efficiency is higher when a low temperature source gas is used than when a high temperature source gas is used. Therefore, by generating ozone using the gas outside the exhaust passage 15 in this way, it is possible to improve the ozone generation efficiency as compared with the case of the publication. The air or oxygen used in the present invention is not limited to the dry state.
  Each of the exhaust control valve V1 and the ozone control valve V2 is a three-way valve that includes a solenoid, and one of the downstream two-way discharge ports can be fully closed and the other can be fully opened. Switch valve.
  The DPFs 30a and 30b are supported via support members (not shown) in substantially cylindrical metal casings 31a and 31b each having a frustoconical shape at both ends. The support member has insulating properties, heat resistance, buffer properties, and the like, and is made of, for example, an alumina mat. The DPF 30a and the ozone supply nozzle 40a, and the DPF 30b and the ozone supply nozzle 40b form units A and B stored in the metal casings 31a and 31b, respectively. In this embodiment, a plurality of such units A and B are arranged in parallel. It will be provided.
  As shown in FIG. 2, the DPFs 30a and 30b are so-called wall flow types including a honeycomb structure 32 made of a porous ceramic, and the honeycomb structure 32 is formed of a ceramic material such as cordierite, silica, or alumina. The The exhaust gas flows from the left to the right in the figure as indicated by the arrows. In the honeycomb structure 32, first passages 34 provided with plugs 33 on the upstream side and second passages 36 provided with plugs 35 on the downstream side are alternately formed to form a honeycomb shape. Yes. These passages 34 and 36 are also called cells, and both are parallel to the flow direction of the exhaust gas. When the exhaust gas flows from the left to the right in the drawing, the exhaust gas passes through the porous ceramic flow passage wall surface 37 from the second passage 36 and flows into the first passage 34 and flows downstream. At this time, PM in the exhaust gas is collected by the porous ceramic, and release of PM into the atmosphere is prevented. A filter type in which exhaust gas passes through the wall surface of the flow path and collects and collects PM at that time is called a wall flow type.
  Similarly to the DPFs 30a and 30b, the NOx catalyst 20 is also supported in a substantially cylindrical metal casing 21 having both end portions formed in a truncated cone shape via a support member (not shown). The support member has insulating properties, heat resistance, buffer properties, and the like, and is made of, for example, an alumina mat.
  The NOx catalyst 20 is preferably composed of either an occlusion reduction type NOx catalyst (NSR: NOx Storage Reduction) or a selective reduction type NOx catalyst (SCR: Selective Catalytic Reduction).
  In the case of the NOx storage reduction catalyst, the NOx catalyst 20 is made of alumina Al.₂O₃A noble metal such as platinum Pt as a catalyst component and a NOx absorbing component are supported on the surface of a base material made of an oxide such as NOx. The NOx absorbing component is at least one selected from, for example, an alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, an alkaline earth such as barium Ba and calcium Ca, and a rare earth such as lanthanum La and yttrium Y. It consists of one.
  The NOx storage reduction catalyst 20 absorbs NOx when the air-fuel ratio of the exhaust gas flowing into it is leaner than a predetermined value (typically the theoretical air-fuel ratio), and the oxygen concentration in the exhaust gas flowing into the NOx catalyst 20 When NO decreases, the absorbed NOx is released by releasing the absorbed NOx. In this embodiment, since a diesel engine is used, the exhaust air-fuel ratio at normal times is lean, and the NOx catalyst 20 absorbs NOx in the exhaust. Further, when the reducing agent is supplied on the upstream side of the NOx catalyst 20 and the air-fuel ratio of the inflowing exhaust gas becomes rich, the NOx catalyst 20 releases the absorbed NOx. The released NOx reacts with the reducing agent and is reduced and purified.
  This NOx absorption / reduction and reduction / purification is considered to be performed based on the following mechanism as shown in FIGS. 3A and 3B. About this mechanism, alumina Al₂O₃An example of an occlusion reduction type NOx catalyst in which platinum Pt and potassium K are supported on the surface of the base material will be described. The same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.
  First, as shown in FIG. 3A, when the inflowing exhaust gas becomes lean, the oxygen concentration and NOx concentration in the inflowing exhaust gas increase.₂Is O₂ ⁻Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the inflowing exhaust gas is O on the surface of platinum Pt.₂ ⁻Or O^2-Reacts with NO₂(2NO + O₂→ 2NO₂). Then the generated NO₂Is absorbed by potassium K, an absorption component, and nitrate, that is, potassium nitrate KNO.₃And absorbed by K. As long as the oxygen concentration in the inflowing exhaust gas is high, NO on the surface of platinum Pt₂Unless NO is absorbed and the NOx absorption capacity of K is saturated₂Is absorbed by K. On the other hand, the oxygen concentration in the inflowing exhaust gas decreases and NO₂When the production amount of NO decreases, the reaction proceeds in the reverse direction (NO₃→ NO₂), So potassium nitrate KNO in K₃Is NO₂Is released from the absorbent in the form of That is, NOx is released from K when the oxygen concentration in the inflowing exhaust gas decreases. If the leanness of the inflowing exhaust gas is lowered, the oxygen concentration in the inflowing exhaust gas is lowered. Therefore, if the leanness of the inflowing exhaust gas is lowered, NOx is released from K.
  On the other hand, when the air-fuel ratio of the inflowing exhaust gas is made rich at this time, HC and CO in the inflowing exhaust gas are oxygen O on platinum Pt.₂ ⁻Or O^2-It reacts with and is oxidized. Further, when the air-fuel ratio of the inflowing exhaust gas is made rich, the oxygen concentration in the inflowing exhaust gas extremely decreases, so that K to NO₂Is released and this NO₂As shown in FIG. 3B, N is reacted with unburned HC and CO using platinum Pt as a reaction window.₂, O₂It can be reduced and purified. In this way, NO on the surface of platinum Pt.₂NO from K to next when no longer exists₂Is released. Therefore, when the air-fuel ratio of the inflowing exhaust gas is made rich, NOx is released from K in a short time and reduced and purified.
  The reducing agent used here may be any substance that generates reducing components such as hydrocarbon HC and carbon monoxide CO in the exhaust gas, and gas such as hydrogen and carbon monoxide, liquid such as propane, propylene, and butane. Alternatively, liquid hydrocarbons such as gaseous hydrocarbons, gasoline, light oil, and kerosene can be used. In this embodiment, light oil, which is a fuel for a diesel engine, is used as a reducing agent in order to avoid complications during storage and replenishment. As a method of supplying the light oil as the reducing agent to the NOx catalyst 20, for example, light oil is injected from a reducing agent injection valve separately provided in the exhaust passage 15 upstream of the NOx catalyst 20, or from the fuel injection valve 14. A so-called post-injection method in which light oil is injected into the combustion chamber 13 in the later stage of the expansion stroke or in the exhaust stroke is possible. The supply of the reducing agent for the purpose of releasing and reducing NOx in the NOx catalyst 20 is referred to as a rich spike.
  Next, in the case of a selective reduction type NOx catalyst, as shown in FIG. 4, the NOx catalyst 20 has a surface of a base material such as zeolite or alumina carrying a noble metal such as Pt, or a surface of the base material such as Cu. A transition metal supported by ion exchange and a titania / vanadium catalyst (V₂O₅/ WO₃/ TiO₂) Can be exemplified. In this selective reduction type NOx catalyst, HC and NO in the exhaust gas are constantly and simultaneously reacted under the condition that the air-fuel ratio of the inflowing exhaust gas is lean.₂, CO₂, H₂Purified like O. However, the presence of HC is essential for NOx purification. Even if the air-fuel ratio is lean, unburned HC is always contained in the exhaust gas, and this can be used to reduce and purify NOx. Further, the reducing agent may be supplied by performing rich spike like the NOx storage reduction catalyst. In this case, ammonia or urea can be used as the reducing agent in addition to those exemplified above.
  Returning to FIG. 1, in the present embodiment, means for detecting the amount of PM trapped or the degree of clogging in the DPFs 30a and 30b is provided. That is, exhaust pressure sensors 51a, 51b, 52a and 52b for detecting exhaust pressure are provided in the exhaust passages 15 upstream and downstream of the DPFs 30a and 30b, respectively, and these are connected to the ECU 100 as control means. The ECU 100 determines the DPF 30a, 30b based on the difference, that is, the differential pressure, between the upstream exhaust pressure detected by the upstream exhaust pressure sensors 51a, 51b and the downstream exhaust pressure detected by the downstream exhaust pressure sensors 52a, 52b. The amount of PM collected or the degree of clogging is determined.
  The upstream exhaust pressure sensors 51a and 51b are arranged downstream of the NOx catalyst 20 and upstream of the ozone supply nozzles 40a and 40b in this embodiment, but are downstream of the ozone supply nozzles 40a and 40b. It may be arranged on the side. In this embodiment, the amount of PM trapped or the degree of clogging is detected by the differential pressure on the upstream and downstream sides of the DPFs 30a and 30b, but is collected only by one exhaust pressure sensor arranged on each upstream side of the DPFs 30a and 30b. The amount or the degree of clogging may be detected. Furthermore, the degree of clogging can also be detected by obtaining the temporal integration of the soot signal of the soot sensor arranged upstream of the DPF. Similarly, engine characteristic map data stored in the ECU relating to soot generation can be evaluated and integrated over time.
  In the present embodiment, means for detecting the air-fuel ratio of the exhaust gas flowing into the DPFs 30a and 30b is provided. That is, an air-fuel ratio sensor (not shown) is provided downstream of the NOx catalyst 20 and upstream of the DPFs 30a and 30b, and the ECU 100 calculates the exhaust air-fuel ratio based on the detection signal of the air-fuel ratio sensor 54. In the present embodiment, the air-fuel ratio sensor 54 detects the exhaust air-fuel ratio upstream of the ozone supply nozzles 40a and 40b. These sensors 51, 52, 53 are all attached to the casing 31.
  The exhaust control valve V1 and the ozone control valve V2 are connected to the output side of the ECU 100, and operate according to the control output of the ECU 100.
  An example of the operation of the present embodiment configured as described above will be described. In FIG. 5, first, the ECU 100 compares the differential pressures A and B for the DPFs 30a and 30b (S10). The differential pressure A for the DPF 30a is calculated by the difference (Pua-Pla) between the detected values Pua and Pla of the exhaust pressure sensors 51a and 52a before and after the DPF 30a. The differential pressure B for the DPF 30b is calculated by the difference (Pub−Plb) between the detection values Pub and Plb of the exhaust pressure sensors 51b and 52b before and after the DPF 30b. It can be considered that the larger the deviations A and B, the greater the amount of PM collected or the degree of clogging.
  As a result of the comparison in step S10, when the differential pressure A <the differential pressure B, it can be considered that the collected amount or the degree of clogging of the DPF 30b is larger. In this case, the ECU 100 next determines whether or not the differential pressure A exceeds a predetermined reference value (S20). In the affirmative case, the ECU 100 controls the exhaust control valve V1 to select the unit A as an exhaust gas supply destination (that is, the exhaust passage on the unit A side is fully opened and the exhaust passage on the unit B side is fully closed). (S30).
  Next, the ECU 100 controls the ozone control valve V2 to select the unit B as the ozone supply destination (ie, fully close the ozone supply passage 42a on the unit A side and fully open the ozone supply passage 42b on the unit B side). Then, the ozone generator 41 is turned on (S40). The supply of ozone to the DPF 30b of the unit B is continuously executed until the differential pressure A becomes equal to or lower than a predetermined reference value. When the differential pressure A is equal to or lower than the reference value, the process of step S40 is skipped.
  Further, when the differential pressure A ≧ the differential pressure B, it can be considered that the collected amount or clogging degree of the DPF 30a is larger. In this case, the ECU 100 next determines whether or not the differential pressure B exceeds a predetermined reference value (S50). If the determination is affirmative, the ECU 100 controls the exhaust control valve V1 to select the unit B as an exhaust gas supply destination (that is, the exhaust passage on the unit A side is fully closed and the exhaust passage on the unit B side is fully opened). (S60).
  Next, the ECU 100 controls the ozone control valve V2 to select the unit A as the ozone supply destination (that is, fully open the ozone supply passage 42a on the unit A side and fully close the ozone supply passage 42b on the unit B side). Then, the ozone generator 41 is turned on (S70). The supply of ozone to the DPF 30a of the unit A is continuously executed until the differential pressure B becomes equal to or lower than a predetermined reference value, and when it is equal to or lower than the reference value, the process of step S70 is skipped.
  The above process is repeatedly executed while the engine is operating (S80), and is terminated on condition that the engine is stopped.
  As a result of the above processing, in the present embodiment, ozone is supplied in a state where the supply of exhaust gas is stopped for the DPF 30a, 30b having a larger amount of PM trapped or clogged. At that time, with respect to the DPF with the smaller amount of PM collected or clogged, the exhaust gas is supplied in the whole amount, but the supply of ozone is not executed.
  As described above, in the present embodiment, the following operational effects are exhibited. In other words, the exhaust control valve V1 is controlled so that the ratio of the exhaust gas supply amount between the plurality of DPFs 30a and 30b can be changed. The consumption of ozone by a predetermined substance such as NOx and HC can be suppressed, and the decomposition of ozone by the heat of exhaust gas can be suppressed. Therefore, ozone can be used efficiently, and the PM purification efficiency by ozone can be improved. Here, “the ratio of the exhaust gas supply amount is reduced” indicates that the ratio of the exhaust gas supply amount is smaller than at least one of the other DPFs.
  Further, since the ozone control valve V2 is controlled so that the ratio of the ozone supply amount to the DPF in which the ratio of the exhaust gas supply amount is made relatively small by the exhaust control valve V1, the ozone consumption and the ozone Can be further suppressed. Here, “relatively increasing the ratio of the ozone supply amount” indicates that the ratio of the ozone supply amount is made larger than at least one of the other DPFs.
  The exhaust control valve V1 can individually fully close the exhaust gas passages for the plurality of DPFs 30a and 30b, and the ozone control valve V2 can individually fully close the ozone passage for the plurality of DPFs 30a and 30b. Therefore, the desired effect of the present invention can be obtained with a simple configuration.
  The ECU 100 further includes a collection amount detection means for individually detecting the collection amounts of the plurality of DPFs 30a and 30b, and the ECU 100 selects a DPF having a low collection amount as the exhaust gas supply destination from the plurality of DPFs 30a and 30b. As a result, PM oxidation removal can be prioritized and executed for DPFs that require high PM removal. Here, “the collected amount is low” indicates a state where the collected amount is lower than at least one of the other DPFs.
  In addition, since the supply of ozone is executed only when the amount of PM trapped or clogged in the DPFs 30a and 30b exceeds a predetermined reference value, the oxidation removal of PM is limited to the case where the necessity is high. It is feasible and can save ozone usage.
  Next, the results of an experiment performed on the first embodiment are shown below.
  (1) Experimental equipment
  FIG. 6 shows an outline of the experimental apparatus. Gaseous oxygen O supplied from the oxygen cylinder 67₂Is branched into two by a flow rate control unit 68, and one of them is supplied to an ozone generator 69. In the ozone generator 69, oxygen is selectively and partially converted into ozone O 3, and these oxygen and ozone (or only oxygen) reach the ozone analyzer 70. In the other branch, oxygen is mixed with the gas supplied from the ozone generator 69 after the flow rate is controlled, and reaches the ozone analyzer 70. In the ozone analyzer 70, the ozone concentration of the gas flowing into it, that is, the supply gas supplied to the DPFs 30 a and 30 b is measured, and then the flow rate of the supply gas is controlled by the flow rate control unit 71. Nitrogen N supplied from nitrogen cylinder 72₂The flow rate is controlled by the flow rate control unit 73 and supplied to the downstream side of the flow rate control unit 71. Excess supply gas is discharged to the outside through an exhaust duct (not shown), and the supply gas whose flow rate is controlled is supplied to the DPF 30a or DPF 30b via the ozone control valve V2.
  Downstream of the DPFs 30a and 30b, an exhaust gas analyzer 77 for measuring HC, CO, and NOx concentrations, an exhaust gas analyzer 78 for measuring CO2 concentrations, and an ozone analyzer 79 for measuring ozone concentrations are respectively provided. It is arranged in series from the upstream side.
  (2) Experimental conditions
  The engine 10 was a 2000 cc diesel engine.
  The pretreatment catalyst 120 is a cordierite honeycomb structure having a diameter of 103 mm, a length of 155 mm, and a cell number of 400 cpsi (cells per square inch), coated with 200 g / L of Ce—Zr composite oxide, and Pt with Ce—Zr composite. What carried 3 wt% with respect to the oxide weight was used.
  As the DPFs 30a and 30b, cordierite DPF (catalyst is not coated) having a diameter of 103 mm, a length of 155 mm, and a cell number of 300 cpsi was used.
  The composition of the supply gas coming out of the ozone generator 69 is 18700 ppm of ozone O3 and the remainder is O₂It is. However, this is a composition in the case of supplying ozone with the ozone generator 69 turned on. When the ozone generator 69 is turned off and ozone supply is not performed, the supply gas is O₂It becomes only. The flow rate of the supply gas is 30 L (liter) / min.
  (3) Experimental method
  The DPF is dried at 150 ° C. for 2 hours in advance and the weight is measured. After the DPF is placed in the exhaust pipe and the exhaust gas is circulated for 30 minutes, the DPF is taken out from the exhaust pipe and dried at 150 ° C. for 2 hours to measure its weight. The difference in weight is defined as the PM accumulation amount. After 30 minutes of exhaust gas flow, the amount of PM deposited when PM oxidation was not performed was 3.1 g / hL.
  For the examples and comparative examples, after 30 minutes of exhaust gas flow, PM oxidation was performed, DPF was taken out from the exhaust pipe, dried at 150 ° C. for 2 hours, and its weight was measured. The PM deposition amount was determined from the difference from the previously determined PM deposition amount.
  For the examples, CO₂When the oxidation rate of PM was estimated from the total amount of carbon measured by the meter and the CO meter, the value agreed with the value obtained by reducing the weight of the DPF within an error range. For the comparative example, CO in the exhaust gas₂High concentration (about 7%), CO generated by PM oxidation for measurement accuracy₂The amount could not be separated and quantified.
  (4) Examples and Comparative Examples / Examples
  The exhaust gas from the engine 10 is allowed to flow into the unit A for 30 minutes, PM is deposited, and then the exhaust control valve V1 is switched to the unit B side so that the exhaust gas does not flow into the unit A to generate ozone. Gas from vessel 69 (O₂+ O₃) N of 120 L / min₂And added to Unit A to oxidize PM for 10 minutes.
  ・ Comparative example
  After exhaust gas from the engine 10 is allowed to flow into the unit A for 30 minutes and PM is deposited, the gas from the ozone generator 69 (O₂+ O₃) Was added to oxidize PM for 10 minutes. Do not dilute with N2. The oxidation rate was calculated considering the amount of PM flowing from the engine during PM oxidation.
  (5) Experimental results
  FIG. 7 shows a comparison of the PM oxidation rate between the example and the comparative example. In the figure, the unit g / hL of the PM oxidation rate on the vertical axis represents the number of grams of PM oxidized per liter of DPF and per hour. As can be seen, the effect of stopping the supply of exhaust gas to the unit A can be seen by comparing the embodiment and the comparative example. That is, when the supply of exhaust gas to the unit A is stopped, PM oxidation by ozone supply is promoted.
  [Second Embodiment]
  Next, a second embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 8 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the second embodiment of the present invention. As shown in the figure, in the second embodiment, a means for detecting the DPF bed temperature of the DPFs 30a and 30b is provided. That is, the DPFs 30a and 30b are provided with temperature sensors 53a and 53b, and the ECU 100 individually calculates the bed temperatures of the DPFs 30a and 30b based on the detection signals of the temperature sensors 53a and 53b. The temperature detectors 53a and 53b (tips in the case of thermocouples) are embedded in the DPFs 30a and 30b to detect the bed temperature inside the DPFs 30a and 30b. May be disposed near the center of the upstream end face of the DPF 30a, 30b. Since the remaining mechanical configuration of the second embodiment is the same as that of the first embodiment, the same reference numerals are given and detailed description is omitted.
  An example of the operation of the second embodiment configured as described above will be described. In FIG. 9, first, the ECU 100 compares the differential pressures A and B for the DPFs 30a and 30b (S110). As a result of the comparison in step S110, when the differential pressure A <the differential pressure B, it can be considered that the collected amount or clogging degree of the DPF 30b is larger. In this case, the ECU 100 next determines whether or not the differential pressure A exceeds a predetermined reference value (S120). If the determination is affirmative, the ECU 100 controls the exhaust control valve V1 to select the unit A as an exhaust gas supply destination (that is, the exhaust passage on the unit A side is fully opened and the exhaust passage on the unit B side is fully closed). (S130). The above process is the same as the process from step S10 to S30 in the first embodiment described above.
  Next, the ECU 100 determines whether the bed temperature Tb of the DPF 30b is within an appropriate temperature range, that is, a temperature range in which ozone can be used efficiently (in the case of a diesel engine, for example, 150 to 250 ° C.) (S140). If the result is affirmative, the ECU 100 controls the ozone control valve V2 to select the unit B as the ozone supply destination (that is, the unit A side ozone supply passage 42a is fully closed and the unit B side ozone supply passage 42b is selected). Are fully opened) and the ozone generator 41 is turned on (S150). Supply of ozone to the DPF 30b of the unit B is continuously executed until the differential pressure A becomes equal to or lower than a predetermined reference value or the bed temperature Tb is out of an appropriate temperature range, and negative in step S120 or S140. In step S150, the process is skipped.
  When the differential pressure A ≧ the differential pressure B, the ECU 100 next determines whether the differential pressure B exceeds a predetermined reference value (S160). If the determination is affirmative, the ECU 100 controls the exhaust control valve V1. The unit B is controlled to select the exhaust gas supply destination (that is, the exhaust passage on the unit A side is fully closed and the exhaust passage on the unit B side is fully opened) (S170).
  Next, the ECU 100 determines whether the bed temperature Ta of the DPF 30a is within an appropriate temperature range, that is, a temperature range in which ozone can be efficiently used (150 to 250 ° C. in the case of a diesel engine, for example) (S180). If the result is affirmative, the ECU 100 controls the ozone control valve V2 to select the unit A as the ozone supply destination (that is, the ozone supply passage 42a on the unit A side is fully opened and the ozone supply passage 42b on the unit B side is opened). The ozone generator 41 is turned on (S190). Supply of ozone to the DPF 30a of the unit A is continuously executed until the differential pressure B becomes equal to or lower than a predetermined reference value or the bed temperature Ta is out of an appropriate temperature range, and negative in step S160 or S180. In step S190, the process of step S190 is skipped.
  The above processing is repeatedly executed while the engine is operating (S200), and is terminated on condition that the engine is stopped.
  As a result of the above processing, in the second embodiment, ozone is supplied only when the DPF bed temperatures Ta and Tb are within the appropriate temperature range, and when the DPF bed temperature Ta and Tb are outside the appropriate temperature range, the ozone supply is performed. Will not be done.
  As described above, in the second embodiment, ozone is supplied only when the DPF bed temperatures Ta and Tb are within the appropriate temperature range, and therefore, PM oxidation removal is limited to the case where this is suitable. Can save the amount of ozone used. In addition, during standby when the DPF floor temperatures Ta and Tb are not within the appropriate temperature range (S140, S180), the supply of exhaust gas to the target DPF is suppressed (S130, S170). When the bed temperature is high, the temperature drop or cooling can be promoted.
  Next, the result of the experiment performed regarding this 2nd embodiment is shown below.
  (1) Experimental equipment
  The experimental apparatus is the same as that of the first embodiment shown in FIG.
  (2) Experimental conditions
  It is the same as that of the first embodiment.
  (3) Experimental method
  It is the same as that of the first embodiment.
  (4) Examples and Comparative Examples / Examples
  The process is the same as that of the first embodiment until the exhaust gas does not flow into the unit A after PM is deposited. In this state, N2 gas is supplied to the unit A to adjust the temperature. While the detected value of the temperature sensor arranged at the DPF inlet (upstream end) is within the range of 5 ° C above and below the target temperature, the gas (O2 + O3) from the ozone generator is added and PM Was oxidized. In the case of 25 ° C., the PM oxidation rate for 10 minutes from the start of introduction of O 3 was calculated.
  (5) Experimental results
  FIG. 10 shows the PM oxidation rate of the example. FIG. 10 shows that there is an appropriate temperature window when PM is oxidized by ozone. That is, PM oxidation is promoted by supplying ozone to a temperature with an appropriate DPF floor temperature in a state where supply of exhaust gas to unit A is stopped.
  [Third embodiment]
  Next, a third embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 11 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the third embodiment of the present invention. As shown in the drawing, the apparatus of this embodiment is provided with means for detecting the DPF bed temperature of the DPFs 30a and 30b. That is, the DPFs 30a and 30b are provided with temperature sensors 53a and 53b, and the ECU 100 individually calculates the bed temperatures of the DPFs 30a and 30b based on the detection signals of the temperature sensors 53a and 53b. The temperature detectors 53a and 53b (tips in the case of thermocouples) are embedded in the DPFs 30a and 30b to detect the bed temperature inside the DPFs 30a and 30b. May be disposed near the center of the upstream end face of the DPF 30a, 30b.
  The NOx catalyst 20 is provided with a temperature sensor 54 for detecting the catalyst bed temperature. In addition, fuel addition injectors (not shown) are provided in the casings 31a and 31b, respectively. The fuel addition injector is preferably arranged as upstream as possible in the casings 31a and 31b, and is used to raise the temperature by supplying the added fuel toward the DPFs 30a and 30b. The fuel addition injector is connected to the output side of the ECU 100 and operates according to the control output of the ECU 100. Since the remaining mechanical configuration of the third embodiment is the same as that of the first embodiment, the same reference numerals are assigned and detailed description is omitted.
  As shown in FIG. 12, in this embodiment, the temperature region is divided into regions A, B, C, and D by reference values Ta, Tb, and Tc, and, as will be described later, according to the temperature region of the DPF. An optimal PM removal method is selected.
  An example of the operation of the third embodiment configured as described above will be described. The processing routine of FIG. 13 is repeatedly executed at predetermined intervals during engine operation. First, the ECU 100 compares the differential pressures ΔP1, ΔP2 for the DPFs 30a, 30b (S201). The differential pressure ΔP1 for the DPF 30a is calculated by the difference (Pua−Pla) between the detected values Pua and Pla of the exhaust pressure sensors 51a and 52a before and after the DPF 30a. The differential pressure ΔP2 for the DPF 30b is calculated by the difference (Pub−Plb) between the detection values Pub and Plb of the exhaust pressure sensors 51b and 52b before and after the DPF 30b. It can be considered that the larger the values of the differential pressures ΔP1 and ΔP2, the greater the amount of PM collected or the degree of clogging.
  If the result of comparison in step S201 is negative, that is, if differential pressure ΔP1 ≧ differential pressure ΔP2, the DPF 30a having a larger collection amount is preferentially regenerated, and in this case, the temperature of the DPF 30a is low. In addition to the regeneration of the DPF 30a, the regeneration of the other DPF 30b is performed (S202 to S221). If the determination in step S201 is affirmative, that is, if the differential pressure ΔP1 <the differential pressure ΔP2, the processing corresponding to the replacement of the DPFs 30a and 30b as in steps S202 to S221 (first, the DPF 30b having a larger collection amount is preferentially used). In this case, when the temperature of the DPF 30b is low, a series of processes in which the other DPF 30a is regenerated in addition to the regeneration of the DPF 30b is performed (S222). Since the contents of the series of processes are simply replacements of the DPFs 30a and 30b in the processes of steps S202 to S221, detailed description thereof is omitted.
  If the result of the comparison in step S201 is negative, that is, if differential pressure ΔP1 ≧ differential pressure ΔP2, it can be considered that the amount of collected DPF 30a or the degree of clogging is larger. In this case, the ECU 100 next determines whether or not the differential pressure ΔP1 exceeds a predetermined reference value ΔP0 (S202). This reference value ΔP0 indicates whether or not PM is clogged in the DPF to require regeneration, and it is considered that regeneration is not necessary when the differential pressure ΔP1 is less than this value. Therefore, in the case of negative in step S202, the process is returned.
  If the determination in step S202 is affirmative, the ECU 100 determines whether the temperature T1 of the DPF 30a detected by the temperature sensor 53a exceeds a predetermined reference value Ta (S203). This reference value Ta is a low temperature side reference value (for example, 100 ° C.) determined in accordance with whether or not PM can be processed with ozone at a speed equal to or higher than a predetermined value.
  If the determination in step S203 is affirmative, since the temperature of the DPF 30a is in the region B, C, or D, the ECU 100 next determines whether the temperature T1 is below a predetermined reference value Tb (S204). . This reference value Tb is determined by the regeneration of ozone with a temperature of PM, NO₂It is a value (for example, 250 ° C.) determined in accordance with whether it is suitable for reproduction according to the above. When the temperature T1 is lower than the reference value Tb, the process proceeds to step S205, and the ECU 100 determines whether the temperature T3 of the NOx catalyst 20 is higher than a predetermined reference T0. If the determination is affirmative, the process proceeds to step S207, and the ECU 100 selects TRAP2, that is, the DPF 30b by the exhaust control valve V1, so that the exhaust gas is supplied to the DPF 30b that is less clogged. Further, the ECU 100 selects the TRAP1, that is, the DPF 30a by the ozone control valve V2, calculates the ozone supply amount based on a predetermined ozone supply amount map, and supplies ozone with the calculated supply amount. Therefore, ozone is supplied to TRAP1, that is, DPF 30a, in a state where exhaust gas is not supplied.
  If NO in step S205, that is, if the catalyst temperature is low, an additional amount of ozone is calculated (S206), and this additional amount is added to the ozone supply amount calculated in the subsequent step S207. For this reason, even when the catalyst temperature is low, NO in the exhaust gas can be purified well.
  The ozone supply amount map is the engine operating state, that is, the relationship between the engine speed and intake air amount, the NOx emission amount and the required ozone amount, the relationship between ozone and PM oxidation rate, and the differential pressure upstream and downstream of the DPF. It is a data table which memorize | stores the relationship between (DELTA) P and PM deposition amount correspondingly. The ECU 100 refers to the ozone supply amount map based on the detected value of the engine speed detected by the crankshaft sensor (not shown) and the intake air amount detected by the air flow meter (not shown), thereby obtaining the required ozone amount. Can be calculated.
  If negative in step S204, that is, if the temperature T1 is in the region C or D, the ECU 100 next determines whether the temperature T1 exceeds a predetermined reference value Tc (S208). This reference value Tc is NO when the temperature is PM.₂Is a high temperature side reference value (for example, 350 to 400 ° C.) determined in accordance with whether it is suitable for regeneration based on the above or regeneration based on fuel addition to the exhaust path.
  If the temperature T1 is lower than the reference value Tc, the process proceeds to step S209, and the ECU 100 selects TRAP1 by the exhaust control valve V1 so as to supply exhaust gas to the DPF 30a that is more clogged. The ozone control valve V2 selects TRAP1, that is, the DPF 30a, calculates an ozone supply amount based on a predetermined ozone supply amount map, and supplies ozone with the calculated supply amount. Therefore, ozone is supplied to TRAP1, that is, DPF 30a in a state where exhaust gas is supplied. Further, in the region C of the temperature at which the process of step S209 is performed, unlike the case of step S207 (region B), the ozone supply amount in the ozone supply amount map is NO generated by the reaction between ozone and NO.₂It is set in consideration of the PM purification speed due to.
  If the temperature T1 exceeds the reference value Tc in step S208, the process proceeds to step S210, and the ECU 100 determines whether the catalyst temperature t3 is greater than the reference value t0. If the result is negative, the process proceeds to step S209. If the result is affirmative, the process proceeds to step S211. In step S211, the ECU 100 selects TRAP1 by the exhaust control valve V1 so as to supply the exhaust gas to the DPF 30a that is more clogged. Further, the ECU 100 stops the operation of the ozone generator 41. Further, the calculation of the fuel addition amount based on the predetermined fuel addition amount map and the addition of the calculated amount of fuel are performed. Therefore, fuel is added to TRAP1, that is, DPF 30a in a state where exhaust gas is supplied.
  Note that the fuel addition amount map takes into account ΔP, which is the differential pressure upstream and downstream of the DPF, and the temperature T, and the engine operating state, that is, the engine speed and intake air amount, the NOx emission amount, and the required fuel addition amount. Is a data table in which are stored in correspondence with each other. The ECU 100 can calculate the required fuel addition amount by referring to the fuel addition amount map based on the detected values of the engine speed and the intake air amount.
  If negative in step S203, that is, if the temperature T1 is below the reference value Ta and is in the region A, it is considered that the regeneration of the DPF 30a cannot be expected to be performed at a speed equal to or higher than the predetermined value. In this case, the process proceeds to step S212, and the ECU 100 selects TRAP2 by the exhaust control valve V1 so as to supply the exhaust gas to the DPF 30b that is more clogged. Further, the selection of TRAP1, that is, DPF 30a by the ozone control valve V2, the supply of ozone at a predetermined maximum supply amount, and the warning output to the driver (for example, a character message on a display device not shown in the passenger compartment) Is displayed). Therefore, ozone is supplied to TRAP1, that is, DPF 30a in a state where exhaust gas is not supplied. The supply of the maximum amount of ozone is continuously performed for a predetermined time, and the processing shifts to step S213 and subsequent steps on condition that the predetermined time has elapsed.
  Further, in the subsequent processing, it is considered that the regeneration processing of TRAP2, that is, the DPF 30b with a smaller degree of clogging, is performed or the processing is performed. First, in step S213, the ECU 100 determines whether the temperature T2 of the DPF 30b detected by the temperature sensor 53b is higher than the predetermined reference value Ta described above (S203).
  If the determination in step S213 is affirmative, since the temperature of the DPF 30b is in the region B, C, or D, the ECU 100 next determines whether the temperature T2 is below the predetermined reference value Tb described above ( S214). When the temperature T2 is lower than the reference value Tb, that is, in the region B, the process proceeds to step S215, and the ECU 100 controls the TRAP1 by the exhaust control valve V1 so as to supply the exhaust gas to the DPF 30a that is more clogged. select. The ozone control valve V2 selects TRAP2, that is, the DPF 30b, calculates the ozone supply amount based on the ozone supply amount map, and supplies the calculated supply amount of ozone. Therefore, ozone is supplied to TRAP2, that is, DPF 30b in a state where exhaust gas is not supplied.
  If negative in step S214, that is, if temperature T2 is in region C or D, ECU 100 next determines whether temperature T2 exceeds predetermined reference value Tc described above (S216).
  When the temperature T2 is lower than the reference value Tc, the ECU 100 next determines whether the catalyst temperature T3 is higher than the reference value T0. If the result is negative, the process proceeds to step S218. If the result is affirmative, the process proceeds to step S219. In step S218, the ECU 100 selects TRAP2 by the exhaust control valve V1 so as to supply exhaust gas to the DPF 30b having a smaller degree of clogging. The ozone control valve V2 selects TRAP2, that is, the DPF 30b, calculates the ozone supply amount based on the above-described ozone supply amount map, and supplies ozone with the calculated supply amount. Therefore, ozone is supplied to TRAP2, that is, DPF 30b in a state where exhaust gas is supplied. Also, in the temperature region C where the process of step S218 is performed, unlike the case of step S215 (region B), the ozone supply amount in the ozone supply amount map is determined by NO2 generated by the reaction between ozone and NO. It is set in consideration of the PM purification rate.
  In step S219, the ECU 100 selects TRAP2 by the exhaust control valve V1 so as to supply exhaust gas to the DPF 30b having a smaller degree of clogging. Further, the ECU 100 stops the operation of the ozone generator 41. Further, the calculation of the fuel addition amount based on the above-described fuel addition amount map and the addition of the calculated amount of fuel are performed. Therefore, fuel is added to TRAP2, that is, DPF 30b in a state where exhaust gas is supplied.
  In the case of negative in step S213, that is, when the temperature T1 of the DPF 30a that is relatively clogged and the temperature T2 of the DPF 30b that is relatively clogged are both in an inactive state lower than the low temperature side reference value Ta. Is determined whether the former differential pressure ΔP1 is smaller than the upper limit reference value ΔPmax of the differential pressure (S220).
  If the result in step S220 is negative, that is, if both the DPFs 30a and 30b are at a low temperature and the differential pressure ΔP1 is greater than the upper limit reference value ΔPmax for the differential pressure, the process proceeds to step S221, and the ECU 100 determines that the DPF 30a TRAP1 is selected by the exhaust control valve V1 so as to supply exhaust gas, and TRAP1 is selected by the ozone control valve V2 so as to supply ozone to the DPF 30a. Furthermore, the ECU 100 instructs a predetermined temperature raising operation such that the temperature T1 exceeds the low temperature side reference value Ta. This temperature raising operation includes, for example, an engine speed increase request and an air-fuel ratio rich spike request to an engine ECU (not shown) for controlling the engine. The ECU 100 also outputs a “warning” warning to the driver (for example, displaying a text message on a display device (not shown) in the passenger compartment).
  If the determination in step S220 is affirmative, that is, if both the DPFs 30a and 30b are at a low temperature and the differential pressure ΔP1 is smaller than the differential pressure upper limit reference value ΔPmax, the process of step S212 is executed again. As a result, the exhaust gas and the maximum supply amount of ozone are supplied to the DPF 30b having a larger degree of clogging, and the purification of PM is promoted.
  As described above, in the present embodiment, the following operational effects are exhibited. In other words, the exhaust control valve V1 is controlled so that the ratio of the exhaust gas supply amount between the plurality of DPFs 30a and 30b can be changed. The consumption of ozone by a predetermined substance such as NOx and HC can be suppressed, and the decomposition of ozone by the heat of exhaust gas can be suppressed. Therefore, ozone can be used efficiently, and the PM purification efficiency by ozone can be improved.
  Further, since the ECU 100 detects the collection amount by the exhaust pressure sensors 51a, 51b, 52a, and 52b and controls the exhaust control valve V1 based on the detected collection amount, there is a high necessity for oxidation removal of PM. With respect to the DPFs 30a and 30b, it is possible to preferentially execute PM oxidation removal, and it is possible to perform appropriate processing according to the amount of collection.
  Further, since the ECU 100 controls the ozone supply means according to the temperatures detected by the temperature sensors 53a and 53b, it is possible to perform appropriate processing according to the temperatures of the DPFs 30a and 30b.
  Moreover, in this embodiment, since the ozone supply means has the ozone generator 41 and the ozone control valve which are a single ozone supply source, the desired effect can be obtained in the present invention with a simple configuration. Can do.
  In this embodiment, the exhaust control valve V1 can individually fully close exhaust gas passages for the plurality of DPFs 30a and 30b, and the ozone control valve V2 can individually fully close ozone passages for the plurality of DPFs 30a and 30b. Therefore, the desired effect can be obtained in the present invention with a simple configuration.
  Further, in the present embodiment, the ECU 100 changes the combination of the DPF selected by the exhaust control valve V1 and the DPF selected by the ozone control valve V2 according to the temperature, and therefore performs an appropriate process according to the temperature. It becomes possible to do.
  Further, in the present embodiment, the ECU 100 sets the ozone supply amount to the DPF to a predetermined maximum amount when the temperature of the DPF having a relatively large collection amount among the plurality of DPFs is lower than the predetermined low temperature side reference value Ta. Then, when the temperature of the DPF exceeds the low temperature side reference value Ta, the ozone supply amount for the DPF is set based on the NOx concentration in the exhaust gas (S212). It becomes possible to do. Here, “the collection amount is relatively large” indicates a state where the collection amount is larger than at least one of the other DPFs.
  Further, in the present embodiment, the ECU 100 converts the DPF having a relatively small collection amount into the ozone control valve V2 when the temperature of the DPF having a relatively large collection amount among the plurality of DPFs is lower than a predetermined low temperature side reference value Ta. Therefore, it is possible to effectively utilize the resources for regeneration such as ozone by preferentially regenerating the DPF having a relatively high temperature. Here, “the collection amount is relatively large” means that the collection amount is larger than at least one of the other DPFs, and “the DPF having a relatively small collection amount” means At least one DPF other than a relatively large amount of DPF is shown.
  In the present embodiment, the ECU 100 stops supplying ozone from the ozone supply source (ozone generator 41) when the temperature of the DPF exceeds a predetermined high temperature reference value Tc. Avoid ozone and use it efficiently.
  In the present embodiment, a fuel addition injector as a temperature raising means is provided upstream of the plurality of DPFs, and the ECU 100 controls the fuel addition injector so that the temperature of the DPF selected by the exhaust control valve V1 is a predetermined high temperature reference. When the value Tc is exceeded, the temperature of the DPF is increased, so that ozone can be efficiently used while avoiding decomposition of ozone at a high temperature. Note that the high temperature reference value as a threshold value for determining whether or not to use the temperature raising means may be different from the high temperature reference value as a threshold value for determining whether or not to stop the supply of ozone.
  The setting of the temperature region and the combination of the DPF selected by the exhaust control valve V1 and the DPF selected by the ozone control valve V2 are not limited to those of the third embodiment.
  Further, although the fuel addition injector is used as the temperature raising means, other means such as a heating wire disposed in and around the DPFs 30a and 30b may be used as the temperature raising means in the present invention.
  In each of the above embodiments, the catalyst device 20 is single, and the exhaust control valve V1 that is a branch point is provided on the downstream side. However, as shown in FIG. 14, for example, the catalyst devices 120a and 120b in the present invention A plurality of them may be arranged in parallel, and an exhaust control valve V1 that is a branch point may be provided upstream of the catalyst devices 120a and 120b arranged in parallel. In each of the above embodiments, a single type of catalyst is used as the catalyst device 20, but a plurality of types of catalysts may be provided in series. Three or more units including the DPF and the ozone supply nozzle may be provided in parallel.
  Moreover, it is good also as conditions for performing PM oxidation that the exhaust gas which flows into DPF30a, 30b does not contain the unnecessary component which produces a reaction with ozone. This unnecessary component is, for example, NOx, and unburned HC reacts with ozone to cause wasteful consumption of ozone. Whether or not such an unnecessary component is contained can be estimated from an exhaust air / fuel ratio detected by installing an air / fuel ratio sensor between the exhaust control valve V1 and the ozone supply nozzles 40a and 40b, for example. . Accordingly, when the ECU 100 determines that an unnecessary component is included based on the detected exhaust air-fuel ratio, the ECU 100 turns off the ozone generator 41 and stops the supply of ozone. On the other hand, when the ECU 100 determines that an unnecessary component is not included, the ECU 100 turns on the ozone generator 41 and supplies ozone.
  In each of the above-described embodiments, the exhaust control valve V1 and the ozone control valve V2 are operated in the two states of fully open or fully closed. Instead of such stepwise change, the exhaust amount in two directions on the exhaust side is reduced. An exhaust control valve and an ozone control valve that can continuously change the ratio may be used.
  Further, in each of the above embodiments, ozone generated by turning on the ozone generator 41 at the time of ozone supply is immediately supplied. However, ozone is generated and stored in advance, and ozone is supplied by switching the valve. It may be. It is also possible to supply ozone by pressurizing it with a pump or a compressor. In each of the above embodiments, a single ozone supply source is used, but a plurality of ozone supply sources may be used.
  In each of the above embodiments, the wall flow type DPF is employed as the PM trapping device, but various other filter structures can be employed. For example, it is an electrostatic collection type straight flow filter, which generates a discharge by applying a DC voltage between a pair of electrodes existing in exhaust gas, and charges the PM negatively, for example. It is adsorbed on the plus side or earth side electrode. Therefore, the PM collection device is formed as an electrode on the plus side or the ground side. In addition to the honeycomb shape as described above, the shape or structure of the substrate may be a plate shape, a cylindrical shape, a pellet shape, a mesh shape, or the like.
  [Fourth embodiment]
  Next, a fourth embodiment of the present invention will be described with reference to the accompanying drawings. In FIG. 15, a diesel particulate filter (hereinafter referred to as DPF) 220 as a particulate matter collecting device for collecting particulate matter (PM) in the exhaust gas is disposed in the exhaust passage 15. In the figure, the DPF 220 is shown in cross section.
  The DPF 220 includes a single metal casing 221, a plurality of (two in this embodiment) filter chambers 110 and 210 that are defined in the casing 221, and filters disposed in the filter chambers 110 and 210, respectively. The members 130 and 230 and the filter chambers 110 and 210 are respectively disposed in the filter chambers, and ozone (O₃) And ozone supply nozzles 140 and 240 as the ozone supply means, and valve means 50 arranged upstream of the ozone supply nozzles 140 and 240 and for switching the filter chambers 110 and 210 into which exhaust gas flows. Has been.
  The casing 221 is provided in the middle of the exhaust pipe 22 that defines the exhaust passage 15, has a substantially cylindrical shape extending in the exhaust gas flow direction, and both end portions 221 a are formed in a truncated cone shape. One filter chamber 110 is provided in the central portion or the central portion in the casing 221, and the other filter chamber 210 is provided in the outer peripheral portion in the casing 221. These filter chambers 110 and 210 are partitioned by a cylindrical partition wall 23 to form a double pipe structure as a whole. Hereinafter, the central filter chamber 110 is referred to as a central filter chamber, and the outer peripheral filter chamber 210 is referred to as an outer peripheral filter chamber. The partition wall 23 is separated from the inlet and outlet of the casing 221 by a predetermined distance. The filter members 130 and 230 are positioned in the center in the axial direction of the central filter chamber 110 and the outer filter chamber 210. Ozone supply nozzles 140 and 240 are provided between the upstream end surface or front end surface of the filter members 130 and 230 and the upstream end or front end of the partition wall 23.
  An ozone generator 41 as ozone generating means is connected to the ozone supply nozzles 140 and 240 via an ozone supply passage 42. The ozone supply passage 42 is bifurcated in the middle, and a switching valve 43 is provided at the branch portion. The switching valve 43 is switched to supply ozone sent from the ozone generator 41 to one of the ozone supply nozzles 140 and 240. Ozone is injected and supplied from the supply ports 141 and 241 of the ozone supply nozzles 140 and 240 toward the filter members 130 and 230 on the downstream side.
  The filter members 130 and 230 are supported in the filter chambers 110 and 210 via a support member (not shown). The support member has insulating properties, heat resistance, buffer properties, and the like, and is made of, for example, an alumina mat.
  As shown in FIG. 16, the filter members 130 and 230 are of a so-called wall-through type including a honeycomb structure 32 made of porous ceramic, and the honeycomb structure 32 is made of a ceramic material such as cordierite, silica, or alumina. It is formed. The exhaust gas flows from the left to the right in the figure as indicated by the arrows. In the honeycomb structure 32, first passages 34 provided with plugs 33 on the upstream side and second passages 36 provided with plugs 35 on the downstream side are alternately formed to form a honeycomb shape. Yes. These passages 34 and 36 are also called cells, and both are parallel to the flow direction of the exhaust gas. When the exhaust gas flows from the left to the right in the drawing, the exhaust gas passes through the porous ceramic flow passage wall surface 37 from the second passage 36 and flows into the first passage 34 and flows downstream. At this time, PM in the exhaust gas is collected by the porous ceramic, and release of PM into the atmosphere is prevented. A filter type in which exhaust gas passes through the wall surface of the flow path and collects and collects PM at that time is called a wall flow type.
  As the ozone generator 41, the form which generate | occur | produces ozone, flowing the dry air or oxygen used as a raw material in the discharge tube which can apply a high voltage, and the other arbitrary forms can be used. The dry air or oxygen used as the raw material here is a gas taken from outside the exhaust passage 15, for example, a gas contained in the outside air, unlike the case of Japanese Patent Laid-Open No. 2005-502823. It is not a gas contained in the exhaust gas inside. In the ozone generator 41, ozone generation efficiency is higher when a low temperature source gas is used than when a high temperature source gas is used. Therefore, by generating ozone using the gas outside the exhaust passage 15 in this way, it is possible to improve the ozone generation efficiency as compared with the case of the publication.
  The ozone supply nozzles 140 and 240 have a plurality of ozone supply ports 41 extending over the entire radial range of the upstream end faces of the filter members 130 and 230 so that ozone can be supplied uniformly to the entire upstream end faces of the filter members 130 and 230. Have. The ozone supply nozzles 140 and 240 are fixed in the casing 221. The ozone supply means may have various forms other than the ozone supply nozzles 140 and 240. For example, when only one ozone supply port 41 is provided, the ozone supply port 41 and the filter member are used. It is preferable that the distance from the upstream end face of 130, 230 is separated by a distance that allows ozone to spread throughout the entire upstream end face.
  The valve means 50 is provided at inlets of the central filter chamber 110 and the outer filter chamber 210, respectively, and a central valve body (first valve body) 151 and an outer valve body (second valve body) that open and close the filter chambers 110 and 210. 251 and a driving device 352 as a driving means capable of driving the valve bodies 151 and 251 so that the valve bodies 151 and 251 open and close alternately.
  As shown in FIG. 17, the central valve body 151 is formed in a circular shape in accordance with the shape of the central filter chamber 110 having a circular cross section, while the outer peripheral valve body 251 is formed in accordance with the shape of the outer peripheral filter chamber 210 having a circular cross section. It is formed in a ring shape. The outer peripheral valve body 251 is equally divided into two parts vertically and is composed of two valve body members 251a and 251b. These valve body members 251a and 251b are opened and closed in a double-folded door or a double-casing window. It is supposed to be.
  As shown in FIGS. 18A and 18B, the driving device 352 includes three rotating shafts 353, 353a, and 353b that are connected and fixed to the central valve body 151 and the valve body members 251a and 251b, respectively. These rotary shafts 353, 353 a, and 353 b extend out of the casing 221 horizontally at the center of the height of the casing 221 and parallel to each other. The rotary shaft 353 is connected and fixed to the center position of the height of the central valve body 151, and the rotary shafts 353a and 353b are connected and fixed to the lower end portion and the upper end portion of the valve body members 251a and 251b, respectively. The centers of the rotation shafts 353, 353a, 353b serve as the rotation center between the central valve body 151 and the valve body members 251a, 251b, and the central valve body 151 and the valve body member are rotated by 90 ° of the rotation shafts 353, 353a, 353b. 251a and 251b open and close. The central valve body 151 and its rotating shaft 353 are offset in the exhaust gas flow direction (shown by arrows in FIGS. 18A and 18B) with respect to the valve body members 251a and 251b and these rotating shafts 353a and 353b, and in particular this embodiment. Is offset downstream.
  As shown in FIGS. 18A and 18B, driven gears 354, 354a, and 354b having the same number of teeth are attached to the rotating shafts 353, 353a, and 353b and connected to a drive source (not shown) such as a servo motor. The drive gears 355 and 355ab are respectively meshed with the driven gear 354 of the central valve body 151 and the driven gear 354a of the upper valve body member 251a. The driven gear 354a of the upper valve body member 251a is meshed with the driven gear 354b of the lower valve body member 251b. The drive gears 355 and 355ab are individually rotated, so that the central valve body 151 and the outer peripheral valve body 251 can be opened and closed independently.
  However, the central valve body 151 and the outer valve body 251 are alternately opened and closed during filter regeneration, which will be described later. That is, as shown in FIG. 18A, when the central valve body 151 is closed, the valve body members 251a and 251b of the outer peripheral valve body 251 are in the open state. In this state, the drive source is operated to rotate the drive gears 355, 355ab as shown in FIG. 18B, and the driven gears 354, 354a, 354b and the rotation shafts 353, 353a, 353b are rotated by 90 ° in the direction indicated by the arrow. The central valve body 151 is opened, and the valve body members 251a and 251b of the outer peripheral valve body 251 are closed.
  As shown in FIG. 15, the ozone generator 41, the switching valve 43, and the drive source of the drive device 352 are connected to an electronic control unit (hereinafter referred to as ECU) 500 serving as a control means. Be controlled.
  In the present embodiment, means for detecting the amount of PM trapped or clogged in the filter members 130 and 230 is provided. Exhaust pressure sensors 61 and 62 for detecting the exhaust pressure are provided at the upstream and downstream end portions 221a of the casing 221, that is, the junctions on the upstream and downstream sides of the two filter chambers 110 and 210, respectively. Based on the exhaust pressure deviation of the upstream exhaust pressure and the downstream exhaust pressure detected by 62, the amount of PM trapped or the degree of clogging in the filter members 130, 230 is determined. In the present embodiment, when the exhaust pressure deviation exceeds a predetermined value, it is determined that both of the two filter members 130 and 230 are clogged, and the PM removal processing, that is, filter regeneration processing of both filter members 130 and 230 is performed at the same timing. To do. However, the exhaust pressure deviation may be detected individually for each of the filter members 130 and 230 or the filter chambers 110 and 210, and the filter regeneration process may be executed individually.
  In the present embodiment, the amount of PM trapped or the degree of clogging is detected by the differential pressure on the upstream and downstream sides of the filter members 130 and 230, but only one exhaust pressure sensor arranged on the upstream side of the filter members 130 and 230. The amount of collection or the degree of clogging may be detected by. Further, the degree of clogging can also be detected by obtaining the temporal integration of the soot signal of the soot sensor arranged upstream of the filter member. Similarly, engine characteristic map data stored in the ECU relating to soot generation can be evaluated and integrated over time.
  Further, an NOx catalyst that purifies NOx in the exhaust gas, an oxidation catalyst that purifies unburned components such as HC and CO in the exhaust gas, and the like may be provided in the exhaust passage 15 upstream of the DPF 220. The NOx catalyst may be an NOx storage reduction catalyst (NSR: NOx Storage Reduction) or a selective reduction NOx catalyst (SCR: Selective Catalytic Reduction).
  The NOx storage reduction catalyst absorbs NOx when the air-fuel ratio of the exhaust gas flowing into it is leaner than a predetermined value (typically the stoichiometric air-fuel ratio), and the oxygen concentration in the exhaust gas flowing into this is reduced. The NOx absorption / release action of releasing the absorbed NOx when the pressure falls is performed. In this embodiment, since a diesel engine is used, the exhaust air-fuel ratio at normal time is lean, and the NOx catalyst absorbs NOx in the exhaust gas at normal time. On the other hand, when the reducing agent is supplied upstream of the NOx catalyst and the air-fuel ratio of the inflowing exhaust gas becomes rich, the NOx catalyst releases the absorbed NOx. The released NOx reacts with the reducing agent and is reduced and purified. Any reducing agent may be used as long as it generates a reducing component such as hydrocarbon HC or carbon monoxide CO in the exhaust gas. Gas such as hydrogen or carbon monoxide, liquid such as propane, propylene, or butane or carbonization of gas. Liquid fuels such as hydrogen, gasoline, light oil and kerosene can be used. In the case of a diesel engine, it is preferable to use light oil, which is a fuel, in order to avoid complications during storage and replenishment. As a reducing agent supply method, for example, light oil is injected from a reducing agent injection valve separately provided in the exhaust passage 15 upstream of the NOx catalyst, or light oil is injected into the combustion chamber 13 from the fuel injection valve 14 in the later stage of the expansion stroke or in the exhaust stroke. It is possible to use a so-called post injection method of injecting the gas. The supply of the reducing agent for the purpose of releasing and reducing NOx in the NOx catalyst is referred to as a rich spike.
  The selective reduction type NOx catalyst reacts HC and NO in the exhaust gas constantly and simultaneously under the condition that the air-fuel ratio of the inflowing exhaust gas is lean,₂, O₂, H₂It purifies like O. The presence of HC is essential for NOx purification. Even if the air-fuel ratio is lean, unburned HC is always contained in the exhaust gas, and this can be used to reduce and purify NOx. Further, the reducing agent may be supplied by performing a rich spike like a NOx storage reduction catalyst. In this case, ammonia or urea can be used as the reducing agent in addition to those exemplified above.
  Oxidation catalyst removes unburned components such as HC and CO₂Reacts with CO, CO₂, H₂A catalyst such as O.
  Since the remaining mechanical configuration of the fourth embodiment is the same as that of the first embodiment, the same reference numerals are given and detailed description thereof is omitted.
  In the exhaust emission control device according to the present embodiment, ozone is supplied from the central ozone supply nozzle 140 to oxidize (combust) the PM deposited on the central filter member 130 or to remove the PM on the outer peripheral side. Ozone is supplied from the ozone supply nozzle 240 to oxidize and remove PM deposited on the outer peripheral filter member 230.
  This will be specifically described. The ECU 500 needs to remove or regenerate PM accumulated on the filter members 130 and 230 when the exhaust pressure deviation between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure sensors 61 and 62 exceeds a predetermined value. Judge. And the drive source of the drive device 352 is operated, and either one of the central valve body 151 and the outer periphery valve body 251 is closed, and the other is opened. In the present embodiment, the filter member 130 on the center side is regenerated first, and as shown in FIG. 19A, the central valve body 151 is closed and the outer peripheral valve body 251 is opened. As a result, the inflow of exhaust gas into the central filter chamber 110 is restricted, and the exhaust gas substantially passes only through the outer peripheral filter chamber 210 and the outer peripheral filter member 230. At this time, the collection of PM in the exhaust gas is performed only by the outer peripheral filter member 230.
  Next, the ECU 500 switches the switching valve 43 to the center side, turns on the ozone generator 41, and supplies ozone generated by the ozone generator 41 from the ozone supply nozzle 140 on the center side. This ozone removes the PM deposited on the filter member 130 on the center side by oxidation.
  When the predetermined time has elapsed, as shown in FIG. 19B, the driving source of the driving device 352 is operated to open the central valve body 151 and close the outer peripheral valve body 251. As a result, the inflow of exhaust gas into the outer peripheral filter chamber 210 is restricted, and the exhaust gas substantially passes only through the central filter chamber 110 and the central filter member 130. Then, the ECU 500 switches the switching valve 43 to the outer peripheral side, starts ozone supply from the ozone supply nozzle 240 on the outer peripheral side, and simultaneously stops ozone supply from the ozone supply nozzle 140 on the central side. Due to the supplied ozone, PM deposited on the filter member 230 on the outer peripheral side is oxidized and removed.
  When the regeneration of the outer peripheral filter member 230 is completed after a predetermined time has elapsed, the ozone generator 41 is turned off to stop the ozone supply, and the driving source of the driving device 352 is operated to open the outer peripheral valve body 251. . As a result, inflow of exhaust gas into the outer peripheral filter chamber 210 is allowed, and the exhaust gas passes through both the central filter chamber 110 and the outer peripheral filter chamber 210, and PM is collected by both filter members 130 and 230. Will be made.
  As described above, according to the exhaust gas purification apparatus according to the present embodiment, the filter chamber on the side to which ozone is supplied is closed by the valve means 50, so that the exhaust gas can be prevented from flowing into the filter chamber and The supplied ozone is prevented from being wasted by NOx, HC, and the like, and a larger amount of ozone can be used for oxidizing and removing the PM deposited on the filter member. Therefore, it becomes possible to improve the purification efficiency of PM by ozone.
  Here, the reaction consumption of NOx and ozone will be described in more detail. Temporarily Ozone O₃And NOx in the exhaust gas, particularly NO, reacts, the reaction equation is expressed by the following equation.
  NO + O₃→ NO₂+ O₂... (1)
  NO produced by this reaction₂Ozone O₃And reacts as follows:
  NO₂+ O₃→ NO₃+ O₂... (2)
  And further the NO produced by this reaction₃Ozone O₃It is decomposed as shown in the following equation.
  2NO₃→ 2NO₂+ O₂... (3)
  Here, paying attention to the equation (1), ozone O is oxidized in NO.₃Is consumed, and if we focus on equation (2), NO₂Ozone to oxidize₃Is consumed. And paying attention to equation (3), NO on the right side₂Is NO on the left side of equation (2)₂Therefore, NO on the left side of this equation (2)₂Ozone to oxidize₃Is consumed.
  Thus, NOx and ozone repeat a chain reaction. Therefore, even if ozone is supplied immediately before the filter members 130 and 230, if NOx is contained in the exhaust gas at that position, a large amount of ozone is consumed for oxidation and decomposition of NOx, and the filter members 130 and 230 are exhausted. The amount of ozone that can be provided to the water will be significantly reduced. Since generation of ozone by the ozone generator 41 requires electric power, such wasteful consumption of ozone leads to wasteful consumption of electric power, which may result in deterioration of fuel consumption.
  On the other hand, when ozone is supplied into the exhaust gas atmosphere where HC exists, ozone O₃Partially oxidizes HC, CO, CO₂, H₂The reaction of producing HC oxides such as O occurs. In this case, ozone cannot be supplied to the filter member by the amount of reaction consumption, and the same problem as described above occurs.
  On the other hand, if the filter chamber on the side to which ozone is supplied is closed as in this embodiment, inflow of exhaust gas into the filter chamber is prevented, and the supplied ozone reacts with NOx and HC. Therefore, it can be effectively used for the oxidation removal of PM of the filter member. Here, only ozone, a raw material for ozone generation, and a gas (such as air) used for dilution of ozone substantially flow in the filter chamber on the side supplied with ozone.
  As another advantage, since the two filter chambers 110 and 210 are arranged adjacent to each other in parallel with the partition wall 23 interposed therebetween, the exhaust gas flowing into the other filter chamber during regeneration of the filter member of one filter chamber. By utilizing the heat of the gas, the temperature of one filter chamber can be maintained within an appropriate temperature range in which PM oxidation by ozone can be effectively performed, and PM oxidation by ozone can be performed with relatively high efficiency.
  In other words, even if the filter member and the ozone supply nozzle are arranged in a single casing and the flow of exhaust gas is stopped and ozone is supplied, the inside of the casing is affected by ozone and outside air as ozone is supplied. It is cooled, and there is a possibility that the temperature is lower than the appropriate temperature range. According to the present embodiment, the heat of the exhaust gas flowing in the other filter chamber can be transmitted to one filter chamber through the partition wall 23, and the temperature of one filter chamber can be suppressed from decreasing. The temperature of one filter chamber can be kept within an appropriate temperature range.
  FIG. 20 shows the relationship between the temperature (horizontal axis) of the filter member to which ozone is supplied and the PM oxidation rate (vertical axis) within a predetermined time. The unit g / hL of the PM oxidation rate on the vertical axis represents the number of grams of PM oxidized per liter of filter member and per hour. As can be seen, as the temperature rises, the PM oxidation rate once peaks at around 150 ° C. and then gradually decreases. And the thermal decomposition of ozone starts from around 300 ° C, and if it exceeds 350 ° C, it becomes difficult to ensure a sufficient PM oxidation rate. From this result, it can be said that the filter member or the ambient temperature thereof is preferably in the range of 150 to 350 ° C. for efficient PM oxidation. In the case of a diesel engine, the exhaust temperature is usually 200 to 300 ° C. or lower, which is suitable for keeping adjacent filter chambers within a temperature range suitable for PM oxidation. Moreover, if the filter chamber on the side to which ozone is supplied is closed as in this embodiment, it is possible to prevent ozone from being decomposed by the heat of the exhaust gas.
  Further, as an advantage of closing the filter chamber on the side to which ozone is supplied, since the gas flow is slow, the contact probability between ozone and PM is increased, the reaction time is increased, and PM oxidation efficiency can be improved. It is done.
  In this embodiment, ozone generated by turning on the ozone generator 41 is supplied immediately when ozone is supplied. However, ozone is generated and stored in advance, and its supply / stop is switched by a valve. Also good. It is also possible to supply ozone by pressurizing it with a pump or a compressor.
  Next, an experiment for confirming the effect of the fourth embodiment was performed, and the result is shown below.
  (1) Experimental equipment
  FIG. 21 shows the entire experimental apparatus. Exhaust gas discharged from the diesel engine 10 sequentially passes through the catalyst 70 and the DPF 220 through the exhaust pipe 22, and then is released to the atmosphere. The catalyst 70 is composed of at least one of the aforementioned NOx catalyst (occlusion reduction type or selective reduction type) and an oxidation catalyst. The switching valve 43 has an ozone gas O₃, Oxygen gas O₂And nitrogen gas N₂A supply gas which is a mixed gas of is supplied.
  Oxygen gas O supplied from the oxygen cylinder 71₂The flow rate supplied to the ozone generator 73 is controlled by the flow rate control unit 72. The remaining oxygen gas bypasses the ozone generator 73. Then, the ozone concentration is measured by the ozone analyzer 74. Thereafter, the flow rate of the mixed gas of ozone and oxygen is controlled by the flow rate control unit 75, and the surplus is discharged to the outside from an exhaust duct (not shown). The mixed gas whose flow rate is controlled is sent from the nitrogen cylinder 76, and the nitrogen gas N whose flow rate is controlled by the flow rate control unit 77 is supplied.₂And the supply gas thus formed is sent to the switching valve 43.
  In the DPF 220, extraction pipes 178 and 278 are inserted and arranged at outlets of the central filter chamber 110 and the outer peripheral filter chamber 210 (on the downstream side of the filter members 130 and 230), respectively. The extraction pipes 178 and 278 are switching valves. The exhaust gas sample in one of the central filter chamber 110 and the outer filter chamber 210 can be extracted. The extracted sample gas includes an exhaust gas analyzer 80 for measuring HC, CO, NOx concentration arranged in series from the upstream side, and CO 2₂Measurement processing is performed by an exhaust gas analyzer 81 for concentration measurement and an ozone analyzer 82 for ozone concentration measurement.
  (2) Experimental conditions
  The engine 10 was a 2000 cc diesel engine. The engine 10 was steadily operated under the operating conditions of a rotational speed of 2200 rpm and a torque of 46 Nm.
  For the central filter member 130, a cordierite filter material (catalyst per square inch) having a diameter of 120 mm, a length of 177 mm, a volume of 2 L (liter), and a cell number of 300 cpsi (cells per square inch) is used. The part was cut by machining to reduce the diameter to 60 mm and placed in the central filter chamber 110.
  For the outer peripheral filter member 230, a cordierite filter material having a diameter of 120 mm, a length of 177 mm, a volume of 2 L (liter), and a cell number of 300 cpsi (no catalyst is coated) is used, and a hole having a diameter of 80 mm is formed in the center of the filter material. The one with a gap was placed in the outer filter chamber 210.
  For the catalyst 70, a cordierite honeycomb structure having a diameter of 103 mm, a length of 155 mm, a volume of 1.3 L (liter), and a cell number of 400 cpsi was coated with a Ce—Zr composite oxide at a coating amount of 200 g / L (however, the denominator). L (liter) of the catalyst means per 1 L of catalyst), and Pt was supported by 3 wt% with respect to the weight of the Ce-Zr composite oxide. Here, if there is no catalyst 70, the amount of unburned HC is large, and this HC and ozone react to affect the PM oxidation rate, so the catalyst 70 was installed.
  As for the amount of ozone added, the mixed gas of ozone and oxygen coming out of the flow rate control unit 75 has an ozone concentration of 18700 ppm, the balance is oxygen gas, and a flow rate of 30 L / min. To this, nitrogen gas at a flow rate of 120 L / min is added. The diluted gas, that is, the supply gas is supplied to the switching valve 43.
  (3) PM oxidation rate calculation method
  The PM oxidation rate was estimated from the total carbon amount measured by the exhaust gas analyzers 80 and 81.
  (4) Examples and comparative examples
  Example 1
  The outer valve body 251 is closed, the central valve body 151 is opened, exhaust gas from the engine is allowed to flow only into the central filter chamber 110, and this state is continued for 30 minutes. During this time, PM is deposited on the central filter member 130. Thereafter, the outer valve body 251 is opened, the central valve body 151 is closed, the filter chamber through which exhaust gas from the engine flows is switched to the outer filter chamber 210, and supply gas containing ozone is supplied to the central filter chamber 110, The PM deposited on the central filter member 130 is oxidized for 10 minutes.
  On the other hand, the reverse operation is performed. That is, the central valve body 151 is closed, the outer peripheral valve body 251 is opened, and the exhaust gas from the engine is allowed to flow only into the outer peripheral filter chamber 210, and this state is continued for 30 minutes. During this time, PM is deposited on the outer peripheral filter member 230. Thereafter, the central valve body 151 is opened, the outer peripheral valve body 251 is closed, the filter chamber through which the exhaust gas from the engine flows is switched to the central filter chamber 110, and supply gas containing ozone is supplied to the outer peripheral filter chamber 210, PM deposited on the outer peripheral filter member 230 was oxidized for 10 minutes.
  Comparative example 1
  In order to clarify the effect of this embodiment in which one filter chamber supplied with ozone is kept warm by the heat of exhaust gas flowing in the other filter chamber, a comparative example as shown in FIG. 22 was used. In addition, the same code | symbol is attached | subjected to the structure same as this embodiment, and detailed description is abbreviate | omitted.
  In this comparative example, the exhaust passage is branched into two via the switching valve 85 on the downstream side of the catalyst 70, and DPFs 186 and 286 are individually provided in these exhaust passages. Therefore, the casings 187 and 287 are also provided separately, and the filter members 188 and 288 and the ozone supply nozzles 189 and 289 are provided in the casings 187 and 287, respectively. The switching valve 85 switches the exhaust passage to one DPF 186 side or the other DPF 286 side. With this configuration, when one DPF is regenerated, the inside of one casing cannot be kept warm by the heat of the exhaust gas flowing in the other casing.
  In this case, the switching valve 85 is switched to one DPF 186 side, exhaust gas is allowed to flow into this for 30 minutes to collect PM, and then the switching valve 85 is switched to the other DPF 286 side, and the one DPF 186 is exhausted. The supply gas was supplied from the ozone supply nozzle 189 so that the gas did not flow, and the PM deposited on one filter member 188 was oxidized for 10 minutes.
  (5) Experimental results
  A comparison of the PM oxidation rates of Example 1 and Comparative Example 1 is shown in FIG. As can be seen, in the case of Example 1, the PM oxidation rate is improved as compared with Comparative Example 1, and thereby the effect of the present embodiment using the exhaust heat becomes clear. In Example 1, there is almost no difference in the PM oxidation rate between the central side and the outer peripheral side.
  [Fifth embodiment]
  Next, a fifth embodiment of the present invention will be described with reference to the accompanying drawings. In addition, about the structure similar to said 1st embodiment, the same code | symbol is attached | subjected in a figure and detailed description is abbreviate | omitted.
  FIG. 24 is a system diagram schematically showing an exhaust gas purification apparatus for an internal combustion engine according to the fifth embodiment of the present invention. As shown in the figure, in the fifth embodiment, temperature sensors 190 and 290 for detecting the temperatures (floor temperatures) of the central filter member 130 and the outer peripheral filter member 230 are additionally provided. These temperature sensors 190 and 290 are connected to ECU 500. The temperature measuring portions (tip portions) of the temperature sensors 190 and 290 are embedded in the center portions of the filter members 130 and 230 in order to accurately detect the temperatures of the filter members 130 and 230.
  The temperature sensors 190 and 290 have temperature measuring units disposed in the central filter chamber 110 and the outer filter chamber 210 on the upstream side of the central filter member 130 and the outer filter member 230, respectively, and flow into the filter members 130 and 230. The temperature of the exhaust gas may be detected.
  Air supply nozzles 191 and 291 as cooling gas supply means for supplying cooling air as cooling gas to the central filter chamber 110 and the outer peripheral filter chamber 210 on the upstream side of the central filter member 130 and the outer peripheral filter member 230, respectively. Is arranged. The configuration of the air supply nozzles 191 and 291 is the same as that of the ozone supply nozzles 141 and 241. In the present embodiment, the air supply nozzles 191 and 291 are provided on the upstream side of the ozone supply nozzles 141 and 241. The air supply nozzles 191 and 291 extend over the entire radial range of the upstream end surfaces of the filter members 130 and 230 so that air can be supplied evenly to the entire upstream end surfaces of the filter members 130 and 230 in the same manner as the ozone supply nozzles 141 and 241. The plurality of air supply ports 192 and 292 are fixed in the casing 221. Note that the form of the cooling gas supply means is not limited to such air supply nozzles 191 and 291, and may be one having only one cooling gas supply port, and a gas other than air is used as the cooling gas. It is also possible.
  An air tank 93 as a cooling gas source is connected to the air supply nozzles 191 and 291 via an air supply passage 94. The air supply passage 94 is bifurcated in the middle, and a switching valve 95 is provided at the branch portion. The switching valve 95 is switched by the ECU 500 so that the air sent from the air tank 93 is supplied to one of the air supply nozzles 191 and 291 or is not supplied at all. Air is injected and supplied from the air supply ports 192 and 292 of the air supply nozzles 191 and 291 toward the filter members 130 and 230 on the downstream side.
  In the fifth embodiment, the air from the corresponding air supply nozzles 191 and 291 according to the temperature detected by the corresponding temperature sensors 190 and 290 when the central filter member 130 or the outer peripheral filter member 230 is regenerated with ozone. Supply is controlled by ECU 500. That is, as described in the first embodiment, the regeneration of the filter member is desirably performed when the filter temperature or the atmospheric temperature is within an appropriate temperature range in which PM oxidation by ozone can be effectively performed. Therefore, according to the fifth embodiment, it is determined whether or not the temperature is within an appropriate temperature range according to the detection values of the temperature sensors 190 and 290, and if within the appropriate temperature range, filter regeneration is executed. If the temperature is not within the appropriate temperature range, the filter regeneration can be stopped. This prevents the supply ozone from being consumed in an inappropriate temperature range.
  For example, taking the regeneration of the central filter member 130 as an example, even if the regeneration timing of the filter member 130 arrives, the ECU 500 detects the detected temperature of the central filter member 130 immediately after a high load operation, for example, at a predetermined upper limit temperature (for example, 350 If it is higher, the supply ozone may be thermally decomposed before reaching the filter member 130. Therefore, the ozone supply is stopped (that is, the ozone generator 41 is not turned on). If the detected temperature of the central filter member 130 is lower than a predetermined lower limit temperature (for example, 150 ° C.), the supply of ozone is stopped because PM oxidation by the supplied ozone may not be performed efficiently. On the other hand, if the detected temperature of the central filter member 130 is in the range of the upper limit temperature or lower and the lower limit temperature or higher, PM oxidation by the supplied ozone can be performed efficiently, so ozone supply from the central ozone supply nozzle 141 is executed.
  On the other hand, when the detected temperature of the central filter member 130 is higher than the upper limit temperature, the ECU 500 switches the switching valve 95 to the central air supply nozzle 191 side, supplies cooling air from the air supply nozzle 191, and controls the central filter member 130. Cooling. As a result, the temperature of the central filter member 130 falls and falls within an appropriate temperature range below the upper limit temperature. In this case, the ECU 500 executes ozone supply from the central ozone supply nozzle 141. The control method as described above is the same for the regeneration of the outer peripheral filter member 230.
  Thus, according to the fifth embodiment, in addition to the same effects as the first embodiment, ozone supply in an inappropriate temperature range, particularly an excessively high temperature, can be prevented, and ozone can be used more efficiently. Can be achieved.
  Since the experiment for confirming the effect was performed also for the fifth embodiment, the result is shown below.
  (1) Experimental equipment
  The same as in the first embodiment.
  (2) Experimental conditions
  Except that the operating condition of the engine 10 is changed to a rotational speed of 2400 rpm and a torque of 77 Nm, it is the same as in the first embodiment. The operating condition on the higher load side here is to increase the exhaust gas temperature. In this operating condition, the exhaust gas temperature reaches 300 tens of degrees Celsius.
  (3) PM oxidation rate calculation method
  The same as in the first embodiment.
  (4) Examples and comparative examples
  Example 2
  The outer valve body 251 is closed, the central valve body 151 is opened, exhaust gas from the engine is allowed to flow only into the central filter chamber 110, and this state is continued for 30 minutes. During this time, PM is deposited on the central filter member 130, and the temperature of the central filter member 130 rises to a relatively high temperature. Thereafter, the outer valve body 251 is opened, the central valve body 151 is closed, the exhaust gas is allowed to flow only into the outer filter chamber 210, and the inflow of exhaust gas into the central filter chamber 110 is blocked. In this state, air is supplied from the central air supply nozzle 191 to the central filter chamber 110, and the temperature detected by the central temperature sensor 190 is controlled to be in the range of 245 to 255 ° C. In this state, a supply gas containing ozone is supplied to the central filter chamber 110, and the PM deposited on the central filter member 130 is oxidized for 10 minutes.
  Comparative example 2
  Comparative Example 2 uses the same experimental apparatus as Example 2, but differs from Example 2 in the following points. That is, after switching the exhaust gas inflow from the outer peripheral filter chamber 210 to the central filter chamber 110, air is not supplied from the central air supply nozzle 191 and the supply gas is supplied to the central filter chamber 110 without temperature control. The PM deposited on the filter member 130 is oxidized for 10 minutes. The temperature at this time was 295-283 degreeC.
  (5) Experimental results
  A comparison of the PM oxidation rates of Example 2 and Comparative Example 2 is shown in FIG. As can be seen, in the case of Example 2, the PM oxidation rate is improved as compared with Comparative Example 2, and thereby the effect of the present embodiment in which ozone is supplied within an appropriate temperature range by air supply becomes clear. .
  As mentioned above, although 4th and 5th embodiment of this invention has been described, this invention can also take other embodiment. For example, as shown in FIG. 26, the filter chambers 110A and 210A may be formed by dividing the inside of the casing 221 into two vertically in a plane along the axial direction. In this case, the above-described components such as filter members 130A and 230A and an ozone supply nozzle (not shown) are arranged in the filter chambers 110A and 210A, respectively. Then, one semicircular valve body 51A is rotated by 180 ° by the rotary shaft 353A corresponding to the filter chamber that supplies ozone, and alternately opens and closes the filter chambers 110A and 210A. When ozone supply is not performed, the valve body 51A is held horizontally, and exhaust gas inflow into both the filter chambers 110A and 210A is allowed. When this vertically split structure and the double pipe structure of the above embodiment are compared, in the case of the double pipe structure, heat transfer from one filter chamber to the other filter chamber can be performed in a wide range in the entire circumferential direction. However, it is more disadvantageous than the vertically-divided structure in that the structure is slightly complicated.
  In the fourth and fifth embodiments, two filter chambers and corresponding components are used, but three or more filter chambers may be used. Moreover, although the wall flow type DPF is adopted as the PM collecting device, various other filter structures can be adopted. For example, it is an electrostatic collection type straight flow filter, which generates a discharge by applying a DC voltage between a pair of electrodes existing in exhaust gas, and charges the PM negatively, for example. It is adsorbed on the plus side or earth side electrode. Therefore, the PM collection device is formed as an electrode on the plus side or the ground side.
  Further, in each of the above embodiments, the operation of the switching valve 43 and the valve means 50 is set to the two states of fully open or fully closed, but instead of such stepwise change, the ratio of the exhaust amount in the two directions on the exhaust side is changed. A switching valve and valve means that can be continuously changed may be used.
  In the above embodiments, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that it is possible. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.
  The present invention can be applied to all internal combustion engines that may generate PM, in addition to a diesel engine as a compression ignition type internal combustion engine. For example, a direct injection spark ignition internal combustion engine, more specifically, a direct injection lean burn gasoline engine. In this engine, fuel is directly injected into the in-cylinder combustion chamber. However, in a high load region where the fuel injection amount is large, the fuel does not completely burn and PM may be generated. Even when the present invention is applied to such an engine, the same effect as described above can be sufficiently expected.

  The present invention can be used to effectively use ozone when oxidizing and removing PM using ozone.

Claims (19)

A plurality of particulate matter collecting devices that are branched and connected to the exhaust passage and collect particulate matter in the exhaust gas;
Ozone supply means capable of supplying ozone to the upstream side of the plurality of particulate matter collection devices,
Control means for changing the ratio of the supply amount of exhaust gas and the ratio of supply amount of ozone between the plurality of particulate matter collection devices,
An exhaust emission control device for an internal combustion engine, comprising: An exhaust emission control device for an internal combustion engine according to claim 1,
An exhaust emission control device for an internal combustion engine, further comprising at least one catalyst device disposed in the exhaust passage upstream of the plurality of particulate matter trapping devices to remove a predetermined substance in the exhaust gas. . An exhaust emission control device for an internal combustion engine according to claim 1 or 2,
A collection amount detection means for individually detecting the collection amount of the plurality of particulate matter collection devices;
Temperature detecting means for individually detecting temperatures of the plurality of particulate matter collecting devices;
Further comprising
The control means controls the ratio of the supply amount of the exhaust gas based on the collected amount detected by the collected amount detection means, and the ozone supply amount based on the temperature detected by the temperature detection means. An exhaust emission control device for an internal combustion engine, wherein the ratio is controlled. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3,
The exhaust gas purifying apparatus for an internal combustion engine, wherein the control means relatively increases a ratio of an ozone supply amount to the particulate matter trapping device in which a ratio of an exhaust gas supply amount is relatively small. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4,
The exhaust gas passages for the plurality of particulate matter collection devices can be individually fully closed, and the ozone passages for the plurality of particulate matter collection devices can be individually fully closed. An exhaust purification device for an internal combustion engine. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 5,
Further comprising a collection amount detection means for individually detecting the collection amount of the plurality of particulate matter collection devices,
The exhaust gas purification apparatus for an internal combustion engine, wherein the control means selects a particulate matter collection device having a low collection amount from the plurality of particulate matter collection devices as an exhaust gas supply destination. An exhaust emission control device for an internal combustion engine according to any one of claims 3 to 6,
The control means includes
Supplying ozone to the particulate matter collection device when the temperature of the particulate matter collection device having a relatively large collection amount out of the plurality of particulate matter collection devices is lower than a predetermined low temperature side reference value. Set the amount to the predetermined maximum amount,
When the temperature of the particulate matter collection device exceeds the low-temperature side reference value, an ozone supply amount to the particulate matter collection device is set based on the NOx concentration in the exhaust gas. Engine exhaust purification system. An exhaust emission control device for an internal combustion engine according to any one of claims 3 to 7,
When the temperature of the particulate matter collection device having a relatively large collection amount among the plurality of particulate matter collection devices falls below a predetermined low temperature side reference value, the control means An exhaust emission control device for an internal combustion engine, wherein a relatively small particulate matter collection device is selected as a supply destination of ozone. An exhaust emission control device for an internal combustion engine according to any one of claims 3 to 8,
The exhaust gas purification apparatus for an internal combustion engine, wherein the control means stops the supply of ozone from the ozone supply means when the temperature exceeds a predetermined high temperature reference value. An exhaust emission control device for an internal combustion engine according to any one of claims 3 to 9,
The plurality of particulate matter collection devices further include a temperature raising means,
The control means controls the temperature raising means to collect the particulate matter when the temperature of the particulate matter collection device selected as an exhaust gas supply destination exceeds a predetermined high temperature reference value. An exhaust gas purification apparatus for an internal combustion engine, characterized in that the temperature of the apparatus is increased. An exhaust emission control device for an internal combustion engine according to claim 2,
A catalyst temperature detecting means for detecting the temperature of the at least one catalyst device;
The exhaust gas purification apparatus for an internal combustion engine, wherein the control means controls the ozone supply means based on a temperature of the at least one catalyst device. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 11,
An exhaust emission control device for an internal combustion engine, comprising an exhaust control valve at a branch point of the exhaust passage, wherein an exhaust control valve capable of changing a ratio of an exhaust gas supply amount among the plurality of particulate matter collection devices. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 12,
The ozone supply means includes an ozone control valve capable of changing a ratio of the amount of ozone supplied from a single ozone supply source among the plurality of particulate matter collection devices. Exhaust purification device. The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
The particulate matter collection device includes a plurality of filter chambers formed in parallel in the exhaust gas flow direction adjacent to each other in a single casing, and filter members respectively disposed in the filter chambers. And valve means for switching the filter chamber into which the exhaust gas flows,
The ozone supply means is disposed in each of the plurality of filter chambers,
The exhaust purification device for an internal combustion engine, wherein the valve means is arranged upstream of the ozone supply means. An exhaust emission control device for an internal combustion engine according to claim 14,
An exhaust purification device for an internal combustion engine, wherein two filter chambers are formed in a central portion and an outer peripheral portion of the casing. An exhaust emission control device for an internal combustion engine according to claim 14 or 15,
The valve means is configured so that exhaust gas does not flow into the filter chamber where ozone supply from the ozone supply means is executed, and exhaust gas flows into the filter chamber where ozone supply from the ozone supply means is not executed. An exhaust gas purification apparatus for an internal combustion engine, wherein the filter chamber is switched. An exhaust emission control device for an internal combustion engine according to any one of claims 14 to 16,
The valve means includes a first valve body that opens and closes a part of the plurality of filter chambers, a second valve body that opens and closes the remaining filter chambers of the plurality of filter chambers, and an ozone supply. Corresponding to the filter chamber in which the first valve body and the second valve body are alternately opened and closed, and driving means for driving the first valve body and the second valve body is provided. An exhaust purification device for an internal combustion engine. An exhaust emission control device for an internal combustion engine according to any one of claims 14 to 17,
At least one temperature detection means for detecting the gas flowing into at least one filter member or the temperature of the filter member, and ozone supply from the ozone supply means corresponding to the filter member according to the detected temperature And an exhaust emission control device for an internal combustion engine. An exhaust emission control device for an internal combustion engine according to claim 18,
A cooling gas supply means disposed between the at least one filter member and the valve means and capable of supplying a cooling gas to the filter member from the upstream side; and the cooling gas supply according to the detected temperature An exhaust purification device for an internal combustion engine, comprising: means for controlling cooling gas supply from the means.

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